Tooth Development and Structure Flashcards
When are the first signs of tooth development in weeks?
6 weeks
List the stages of tooth development.
- Bud stage
- Cap stage
- Bell stage
- Late bell/crown stage
What are the 2 embryological tissue derivatives of dental tissue?
Ectoderm and mesenchyme
What are the 3 stages in dentinogenesis?
- Cytodifferentiation
- Matrix formation
- Mineralisation
What occurs in matrix formation of dentinogenesis?
Odontoblasts produce predentine and then retreat inwards
What forms the dentinal tubules?
The long cell processes of odontoblasts
What cell form odontoblasts during cytodifferentiation?
Dental papilla cells
Define amelogenesis.
Formation of enamel
True or False: During amelogenesis, the enamel protein matrix secreted by ameloblasts takes a long time to mineralise.
False, mineralisation of enamel protein matrix is virtually immediate
At what percentage of mineralisation is enamel considered ‘immature enamel’?
30%
Why are deciduous teeth (baby teeth) whiter than adult teeth?
Enamel isn’t formed properly and is white as opposed to enamel that is formed to last a long period of time and is translucent, like on adult teeth
What is the function of Hertwig’s epithelial root sheath?
Drive root development
What percentage of enamel is inorganic?
96%
Describe the amelodentinal junction.
The junction between the enamel and the dentine of a tooth.
List the properties of enamel.
2mm thick
Hard but brittle
Translucent
Covers anatomical crown
What is dentine?
A specialised C.T. consisting of 20% organic material like collagen that is strong and resilient and contains tubules
What covers the root of a tooth?
A mineralised C.T. called cementum
What property of cementum makes orthondontics possible?
Resistance to reabsorption
Why is ground section histological examination better than a decalcified section?
Enamel is present
What is the structure of enamel?
Prisms of tightly packed hydroxyapatite crystals in the core and then less tightly packed crystals in the sheath allowing for space for organic compounds
What is the name for the incremental growth lines in enamel?
Striae of Retzius
What are perikymata?
Shallow furrows where striae of Retzius reach the surface
How do collagen fibres in dentine give strength?
Lie parallel to the amelodentinal junction
What are the contents of dentinal tubules?
Cell processes
Nerves
Fluid
Dentine is highly innervated. Where are most of the nerves located?
Pre-dentine and inner dentine in the pulp horns
Describe the 3 types of dentine classifications.
- Primary: during tooth development up to root completion
- Secondary: After root completion
- Tertiary: Response to pulpal insult
True or False: Acellular cementum is found closer to the enamel while cellular cementum lies below the tooth root.
True
What makes pulp different to connective tissue?
Specialised cells - odontoblasts
Contained in a rigid chamber
Blood vessels with no valves
Densely innervated
What are the layers of pulp from most peripheral?
- Odontoblast layer
- Cell-free zone of Weil
- Cell rich zone
- Pulp core
What percentage of the pulpal innervation is unmyelinated?
70-80%
What are the 2 sensations of myelinated fibres in the pulp?
Pain and pressure
What is the plexus of Raschkow?
Section of pulp in the zone of Weil that monitors painful sensations
Where is the marginal plexus found?
Around odontoblasts in the pulp
